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      <td class="header">&nbsp; DEM Assisted Coregistration<br>
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<h3>DEM-Assisted Coregistration (Back Geocoding)</h3>

<p class="MsoNormal"><span>This operator co-registers two two or more products using the
orbits of the products and a Digital Elevation Model
(DEM).<br>
</span></p>


<h4>Input <br>
</h4>

<ul>


<li>The user should run Apply Orbit File to correct the orbits in all
products. This step can be skipped if no precise or restitude orbit
file
is available. Otherwise this step is always recommended in order to
achieve a better co-registration result.<br>
</li>
</ul>

<h4>Output <br>
</h4>

<ul>

<li>The output of the operator are the co-registered reference and secondary
bands in I/Q format. <br>
</li>
</ul>

<h4>Parameters Used<br>
</h4>

<ul>

<li>Digital Elevation Model: The DEM type. Currently the following
DEMs are supported<br>
</li>
<ul>
<li>ACE2_5min</li>
<li>ACE30</li>
<li>ASTER 1sec GDEM<br>
</li>
<li>GETASSE30</li>
<li>SRTM 1Sec Grid</li>
<li>SRTM 3Sec</li>
<li>user provided external DEM file<br>
</li>
</ul>
<li>DEM Resampling Method: Interpolation method for obtaining
elevation values from the original DEM file. The following
interpolation methods are available</li>
<ul>
<li>nearest neighbour</li>
<li>bi-linear</li>
<li>cubic convolution</li>
<li>5-points bi-sinc</li>
<li>11-points bi-sinc</li>
<li>21-points bi-sinc</li>
<li>bi-cubic<br>
</li>
</ul>
<li>Resampling Type: Interpolation methods for obtaining pixel values
from the source image. The interpolation methods available are the same
as listed above.</li>
<li>Mask out areas with no elevation:&nbsp; Checkbox indicating if
areas without elevation should be masked out from co-registration. It
is recommended to select this checkbox to avoid artefacts along the
coast in the co-registered images.<br>
</li>

</ul>

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